Fine grinding technology use in the mineral processing industry has increased over the last 10 years. This can be mainly attributed to processing finer grained mineral structures, which requires a finer grind for valuable mineral liberation. An ore body requires wide process adaptability and flexibility to cope with the life of mine ore variability.
A grinding process begins typically with a regrinding circuit feed material being pumped to a scalping cyclone upstream of the mill which classifies the target size material off from the feed and defines the milling density. The defined underflow in optimal milling density is pumped into the mill. The slurry enters a grinding chamber containing grinding media (beads) and rotating discs which provide momentum to stir the charge against a series of stationary counter discs. The particles are ground by attrition between the beads. As the flow transfers upwards, the ore slurry passes through the rotating discs and the free space between the static counter discs lining the wall. Depending on the application there may be up to 30 sets of rotating and static discs. Due to the vertical arrangement of the mill, classification is conducted simultaneously throughout the grinding process with larger particles remaining longer at the peripheral, while smaller particles move upwards. The process is typically a single pass with no external classification necessary. Gravity keeps the media compact during operation, ensuring high intensity inter-bead contact and efficient, even energy transfer throughout the volume. Gravity together with an internal hydro classifier prevents the grinding media from escaping the mill by pushing the grinding beads back down into the milling process, and lets through only the fine ground slurry. The disc configuration and the whole chamber geometry have been optimized for efficient energy transfer to the bead mass, internal circulation and classification. With the grinding media evenly distributed, the ore particles remain in constant contact, significantly increasing grinding efficiency. The product discharges at atmosphere at the top of the mill. The combined cyclone overflow and mill discharge are the circuit product.